This allows the demuxer to forward sections of interest downstream, for example SCTE 35 splice information. These can then be reinjected appropriately by a muxer for example. Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/913>
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/913>